Quality ControlAll our lenses are hand figured in the final phase by our master optician, Mr. Csaba Almasi. Before assembling a lens, he interferometrically checks every surface against very high precision test surfaces, to be within tight tolerances both in regards of perfect curvature radiuses and perfectly spherical surfaces.After assembling a lens, it is first double-pass Ronchi tested for quick reference. If the Ronchi test gives perfect results, then the lens is similarly tested with a Foulcault knife-edge test using our very high quality (Zeiss) reference flat mirror. If the figure of the lens is perfect, then it is also checked for color correction (still in double-pass mode) with a bright artificial star. If the lens produces zero color and the wavefront looks perfect, then it receives a unique serial number and it is (optionally) built into a telescope tube. If the customer requested, then it goes to our hungarian sub-contractor for laser-interferometric testing using their internationally calibrated (532nm) interferometer. | |
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When we get back the scope, it is still not ready to go to the customer, because no optics can leave us without personally star testing them by our optical engineer and directing manager, Mr. Pal Gyulai. He compares the results of the interferometric test to the results of his actual star test, and if the two tests would ever happen to contradict each other (this has never happened yet, but mathematically the chance is not zero!), then this would indicate a possible error of our sub-contractor when interferometrically testing the lens (e.g. lens serial numbers swapped, etc.). If this would ever happen, the scope would be re-tested interferometrically.
The interferometric test is the only phase of the production which is done by a sub-contractor, and we take special care to double-check their work. Only practically perfect optics can leave us, there are no exceptions. |
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The above image shows a comparison of multilayer anti-reflection coating of the GPU 127/1200 lens compared to other optics.
The RR achromat on the left side has 2 members with a single air space, the coating applied on the surfaces of this lens is a standard (1 layer) T-coating. In comparison, the significantly smaller amount of reflected light on the 6 surfaces of the TMB triplet apochromat is rather impressive. But the 127mm GPU oil spaced triplet lens (on the right) with its wide-band 7 layer multi-coatings and only 2 air-to-glass surfaces transmits light the most efficiently. Andras Papp (Hungary) | |